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Earth Collides Head-On with Small Comet

January 24, 2013

Sunnyvale record of the January 17 fireball. The beginning of the meteor trajectory is visible right of the bright flash that originated well below the field of view. Click for full size. Credit: Peter Jenniskens

The fireball that lit up the predawn Northern California sky last week was a small comet that hit Earth head-on when it hit the Earth's atmosphere, a researcher said.

The very beginning part of the fireball was captured by all three stations of the Cameras for Allsky Meteor Surveillance (CAMS) project, which enabled the calculation of the trajectory and orbit of this object through triangulation. Because it was fast and bright, the object could already be spotted when it still was 146 km height, a record for CAMS. The CAMS cameras tracked it down to 134 km altitude. The object moved against the motion of the planets on a comet-like orbit.

The comet "instantly turned into dust and gas," resulting in the flash of light seen by many at 5:21 a.m. last Thursday, said meteor astronomer Peter Jenniskens, a scientist at the Seti Institute in Mountain View. "Because the comet vaporized, no pieces fell to Earth," Jenniskens said.

The comet came into contact with the Earth's atmosphere just north of Yosemite National Park at a speed of 160,000 mph, Jenniskens said. "Moving toward Lake Tahoe, the small comet then penetrated to lower elevations where it fully disrupted in the atmosphere," Jenniskens wrote Tuesday on his group's website. The sight was a treat for those up and about before dawn.

Reports of the sighting came in from around California and from outside Reno.

It was the second cosmic sighting in the Bay Area in three months. On Oct. 17, a monster fireball lit up the skies, and several chunks of it - meteorites - were later found in the Novato area.

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